ECE is about electronics and how the different electrical components (Microprocessor, RAM etc) communicate with each other. IT has more physics in it. There is a little programming involved but not much.
CSE deals with telling these components what to do and when to do it; by programming them. It has a lot of logic involved and maths too.
Eg :- In designing a tablet/ phone, all the hardware work is done by the ECE people and all the software stuff (making the different components like RAM , processor talk to each other, and the Operating system ) is done by the CSE people . Both are inter-dependent.
Placement wise, ECE is a little better than CSE as it has more offers in the public sector (govt jobs). Also ECE is considered to be somewhat of a ‘evergreen’ branch. If you do specialisation (eg MTech in VLSI design ) after doing B.tech in ECE, there is a great demand in the market for such people ;le. ECE person can also get a fob in IT ; but this is not the same level as a job a CSE engineer can get. Eg: Intel, AMD, BHEL (and many other govt companies )