A sentence is a group of words‏‎ beginning with a capital letter‏‎ and ending with a full stop/period, exclamation mark or question mark.

It is the written equivalent of an utterance‎.
My name is Conan.
We won!
Is July going to be hot here?

Sentence Types
There are a number of different sentence types in English‏‎ and we use them for different purposes.
Statements
To give information…