Main topics covered in the CBSE Class 10 English Grammar syllabus are as follows:

1. Parts of Speech:
- Noun: Common, Proper, Countable, Uncountable, Collective, etc.
- Pronoun: Personal, Possessive, Reflexive, Demonstrative, Interrogative, etc.
- Adjective: Descriptive, Quantitative, Demonstrative, Possessive, etc.
- Verb: Transitive, Intransitive, Regular, Irregular, etc.
- Adverb: Manner, Time, Place, Degree, etc.
- Preposition: Simple, Compound, Phrase, etc.
- Conjunction: Coordinating, Subordinating, Correlative, etc.
- Interjection: Expressing emotions, feelings, etc.

2. Tenses:
- Present Tense: Simple, Continuous, Perfect, Perfect Continuous.
- Past Tense: Simple, Continuous, Perfect, Perfect Continuous.
- Future Tense: Simple, Continuous, Perfect, Perfect Continuous.

3. Active and Passive Voice:
- Formation and conversion of sentences from active to passive voice and vice versa.
- Appropriate usage of active and passive voice in different situations.

4. Direct and Indirect Speech:
- Formation and conversion of sentences from direct to indirect speech and vice versa.
- Changes in pronouns, verb tense, adverbs, etc. while converting speech.

5. Subject-Verb Agreement:
- Agreement of subject and verb in terms of number and person.
- Identification and correction of errors related to subject-verb agreement.

6. Sentence Transformation:
- Changing sentences from affirmative to negative, interrogative to assertive, etc.
- Formation of compound, complex, and compound-complex sentences.

7. Articles:
- Usage of definite and indefinite articles (a, an, the) in different contexts.
- Omission and correct placement of articles in sentences.

8. Active and Passive Voice:
- Formation and conversion of sentences from active to passive voice and vice versa.
- Appropriate usage of active and passive voice in different situations.

9. Sentence Correction:
- Identification and correction of grammatical errors in sentences.
- Punctuation rules, capitalization, and correct usage of words.

10. Vocabulary and Word Usage:
- Synonyms, antonyms, homonyms, and idioms.
- Understanding and using appropriate words in sentences.

Remember that this is just an overview of the main topics covered in the CBSE Class 10 English Grammar syllabus. Each topic has several subtopics and concepts to be thoroughly understood and practiced. Regular practice and understanding of these grammar rules will help students enhance their language skills and improve their overall proficiency in English.