HI, Before trying to understand the concepts focus on CORE subjects and then work on it systematically. 

In ECE the core subjects are:

1.EDC

2.Analog electronics

3.Signal & Systems

4.Control Systems

5.Network theory

6.Analog & Digital communication

7.Digital Electronics

8.EMFT

9.Microprocessor

10. Electromagnetic theory and transmission lines

This stream is a subtle combo of electronics studies and communication Engg. You shall study all the topics mentioned above. These are important ones too.

Electronics There are two parts: Analog and Digital Electronics. It deals with circuits comprising of discrete components like resistors,capacitors, transistors, every circuit from the basic. The behaviours of those circuits are being observed.

Communication  has Analog and Digital. Analog communication is about transmitting data as a continuous signal rather than in form of discrete levels. There are different communication networks like Wifi, LAN, Mobile Networks, etc.

Signals and Systems For all the above we need signals. We learn about their different representations, operations and their behaviour through a system. After we have processing subjects like Digital Signal Processing and Image processing involving computer tool and whose programming is almost similar to C.

Control Systems This subject basically tries to estimate(not a correct word to use) the behaviour of system from its function rather than much going into the inner details of system. It decides the range of inputs that can be provided to the system so that it works fine.

So this is how I can help you. Rest you will have to work for yourself. Good Luck.