Class 10th

Coordinating conjunctions connect clauses of equal grammatical weight (e.g., two independent clauses) whereas Subordinating conjunctions (like because, although, while) connect an independent clause to a dependent clause and show the relationship between them (cause, time, contrast, etc.).
Example (Coordinating): He was tired, yet he kept running.
Example (Subordinating): Although he was tired, he kept running.

Yes, in informal speech or writing, conjunctions may sometimes be omitted for brevity.

Conjunctions are used to connect words, phrases, or clauses, allowing us to express more complex and meaningful thoughts in a simpler and smooth way.

While writing a precis text, the following are not applicable

• Use of jargons and abbreviations
• Use of own opinion or criticism
• Statements in question format

A good precise writing should follow the below guidelines to avoid errors:

• The sentence must be short and clear
• Use easy words which are easy to understand
• It should be written in own words
• It must be 1/3^rd of the original text

Generally a precise writing in written in present tense only if the event has not ended. Also, precise must be written in reported or indirect speech i.e., in third person (he, she, it, they).

The precise writing helps in providing text briefly and as clear as possible. The important ideas are provided and the irrelevant information are cut down. Precise text provides the central ideas and saves time from reading long texts. 

Precis writing is summarizing the text in brief by keeping the key details intact without any personal ideas or jargons. While writing precisely, certain rules must be followed to cover only important aspect in the text.