If your flying under Visual Flight Rules (VFR) you navigate visually and “see and avoid” obstacles such as terrain and other aircraft. But what does this mean?
In a short, you are in full control of separation between terrain and other pilots. If you see mountains ahead of you and the MSA in that area is 3000ft and you are cruising at 2500ft then it is up to you to climb to an altitude at or above 3000’ to avoid losing separation with terrain.
The same goes for other pilots, the separation you need to maintain between you and other pilots is 3nm horizontally and 500’ vertically. They will need to give other aircraft the right of way.
Unless stated otherwise, if ATC gives you vectors to de-conflict with IFR traffic, you must follow them until you are told to you can resume your own navigation, you must see and avoid other traffic by maintaining the appropriate separation.