Subjects and predicates are two parts that make up a sentence.
Raju is running.
Raju is the subject in this sentence, since it talks about him. Who is running? That is, who is carrying out the verb or action mentioned in the sentence? The answer is Raju.
The lion is running after the deer.
The lion is the subject here. The verb is running, so who is running? The answer is the lion.
Raju is running.
What is the subject Raju doing? He is running. So “is running” becomes the predicate, since it shows what the subject is doing.
The lion is running after the deer.
What is the lion, the subject doing? He is running after the deer, where the deer is the object. Hence “is running after the deer” becomes the predicate since it talks about what the subject is doing.