An object in grammar is something or someone that receives the action of a verb. Think of it like a present you give to someone. The verb is the action of giving, and the object is the present you give.
For example, in the sentence "The dog chases the cat," the verb is chases and the object is the cat. The cat is receiving the action of being chased.
Another example is "Mom bakes a cake for my birthday." The verb is bakes and the object is the cake. The cake is something that is being made for the birthday celebration.
Basically, the object is the thing or person that is being acted upon in a sentence.