Hello Rohith,
ECE is Electronics and Communication Engineering. It is a combination of core electronics along with communication or telecommunications engineering. It mainly deals with the applications of different electronic devices which run using software applications. After B.Tech in ECE, you can do masters in this field by appearing for GATE exam or for planning to study MS. ECE covers topics like VLSI design, signal processing, digital processing, circuits and transmission lines, etc.
This field has found its scope in two broad areas known as telecom industries and software companies. Companies related to aviation, manufacturing of electronics, radio, TV hire ECE candidates. Few of the renowned companies are Reliance Jio, L&T Infotech, Samsung, Infosys, TCS, Tech Mahindra, Accenture, Wipro, etc . Also there are opportunities in government sector, for example, BSNL, BHEL, DRDO, ISRO, DMRC.
The probable job titles are network planning engineer, service engineer, electronics and Communication consultant, field test engineer, Research and Development  Software Engineer. The salary packages vary as per the capability of students and also the college where you are currently studying your B.Tech.
To get admission for ECE in UG, you need to give JEE Mains, which is conducted on a national basis. The score in JEE will determine the college for you and then you can opt for ECE.
I hope that the above provided information is helpful for you. If you have any more queries, do write them in comments section.
All the best...!!!