Some sentences are short and choppy.
Sentences that have ideas that go together can be joined with a comma (,) and the word and.
The river is beautiful. It is useful.
The river is beautiful, and it is useful.
Strawberries grow in fields. They can be picked in the summer.
Strawberries grow in fields, and can be picked in the summer.
I read my book on the grass. My brother tried to read it too.
I read my book on the grass, and my brother tried to read it too.