The phrase(s) for "to give" are a bit complicated in Japanese.

So much so that they qualify as JLPT N5 grammar points.

Today we're looking at one of these phrases:

JLPT N5: あげる (to give [when the speaker is the giver])

Let's say I gave a pair of sunglasses to my grandpa. That would be:

おじいちゃんにサングラスをあげた。
おじいちゃん　に　サングラス　を　あげた。
I gave my grandpa a pair of sunglasses.
Literally: "grandpa + に + sunglasses + を + gave."

Since I am the person who is giving, I use the verb あげる.

HOWEVER, if the person doing the giving is not me (or someone psychologically close to me), then I CANNOT use あげる：

× 先生はわたしに鉛筆をあげました。
× せんせい　は　わたし　に　えんぴつ　を　あげました。
My teacher gave me a pencil.
Literally: "teacher + は + I + に + pencil + を + gave."

Saying あげる is not allowed in this sentence, because the speaker is not the person who gave something. In a case like this, where the person doing the giving is an "outside group" person, then we would use the verb くれる, which we'll have another N5 lesson on in the future:

先生はわたしに鉛筆をくれました。
せんせい　は　わたし　に　えんぴつ　を　くれました。
My teacher gave me a pencil.
Literally: "teacher + は + I + に + pencil + を + gave."

Last but not least, we can use あげる if the giver is a person in my "inside group" and the receiver is in a psychologically distant group, an "outside group." For example, I could use あげる to say that my older sister (psychologically close to me) gave something to my teacher (psychologically more distant than my sister):

お姉ちゃんは先生にリンゴをあげました。
おねえちゃん　は　せんせい　に　りんご　を　あげました。
My sister gave the teacher an apple.
Literally: "older sister + は + teacher + に + apple + を + gave."
Note: One of my favorite words when written in kanji is 林檎 (りんご // apple). I just think it looks cool for some reason. You'll never see it on a JLPT test because the second kanji is not a general-use character (though all Japanese adults seem to be able to read this word).

This is a good chance to point out the particles we use when making a sentence like this:

A は　B に　C を　あげる。
A gives C to B.

A is the giver. B is the recipient. C is the thing that is given.

It might help to look at it this way:

A は
B に
C を
あげる。

So if I want to say, "I give Robert a present," that would be:

I は
Robert に
present を
あげる。

わたしはロバートにプレゼントをあげる。
わたし　は　ロバート　に　プレゼント　を　あげる。
I give Robert a present. // I give a present to Robert.
Literally: "I + は + Robert + に + present + を + give."

As is the case in just about any Japanese sentence, you can remove A, B, or C if any of them are already clear from context. You may recall that our very first example removed A:

おじいちゃんにサングラスをあげた。
おじいちゃん　に　サングラス　を　あげた。
I gave my grandpa a pair of sunglasses.
Literally: "grandpa + に + sunglasses + を + gave."

To recap:

I am the giver → あげる
Someone close to me is the giver → あげる
Someone far from me is the giver → くれる

Here is another example:

今年のクリスマスは子供に子犬をあげるんです。
ことし　の　クリスマス　は　こども　に　こいぬ　を　あげる　んです。
This year we're going to give the kids a puppy for Christmas.
Literally: "this year + の + Christmas + は + child + に + puppy + を + give + んです."

Seem easy enough? I hope so, because now we're leveling up...

When we give something to someone who is a "social superior" (e.g. a boss, the emperor, etc.), then we change あげる to さしあげる.

In other words, you can use this word to appear humble/very polite.

You'll sometimes see this written in kanji: 差し上げる (さしあげる). But you shouldn't use kanji when using regular old あげる.

Example:

優勝した方には賞金100万円をさしあげます。
ゆうしょう　した　かた　に　は　しょうきん　ひゃく　まん　えん　を　さしあげます。
We will give a 1-million yen prize to the winner.
Literally: "victory + did + person + には + prize money + 1 million yen (= 100 x 10,000 yen) + を + give."

部長に誕生日プレゼントをさしあげましょうよ。
ぶちょう　に　たんじょうび　プレゼント　を　さしあげましょう　よ。
Let's give the section chief a birthday present.
Literally: "section chief / director of a department + に + birthday + present + を + let's give + よ."

On the opposite end of the spectrum, we can use やる instead of あげる when talking about giving to recipients that are lower in status than we are.

Typically this is reserved for animals:

A:
マルコさんはわんちゃんにどんなエサをあげていますか。
マルコさん　は　わんちゃん　に　どんな　エサ　を　あげていますか。
What kind of food do you give your dog?
Literally: "Marco-san + は + doggy + に + what kind of + food (for animals) + を + give + か."

B:
色々です。今日はドッグフードと鶏肉をやりました。
いろいろ　です。　きょう　は　ドッグフード　と　とりにく　を　やりました。
All types of food. Today I gave him dog food and chicken.
Literally: "varied + です. + today + は + dog food + と + chicken meat + を + gave."

However, it can also be used, for example, when describing to an "outside group" person how you gave something to a person in your "inside group."

Example:

うちに遊びに来た姪にお小遣いをやった。
うち　に　あそび　に　きた　めい　に　おこづかい　を　やった。
I gave some money to my niece that came to see us.
Literally: "home / my family + に + came to play + niece + に + pocket money + を + gave."

If all of this seems confusing, I wouldn't fret over it. These words are so common that you'll master them via exposure in time.