when we use capital letter

First letter of a sentence First letter of a Name

When we start any sentence then we write the first letter of it in capital letter. For ex:- He is a good boy. In addition, if we write the name of any proper noun then we write the first letter of it in capital letter. Ex:- Earth, Ram,Himalaya, etc.

Hello English Article 25047:English Capitalization Rules https://helloenglish.com/article/25047/English-Capitalization-Rules