One engine Vs Two engines?

Hi everyone,

I have a technical question which you might be able to help me with:

What are the relative advantages of having two engines as opposed to one ?

Is there a possibility of making it back to an airfield on one engine if the other one dies out ?

What prompts an aircraft manufacturer to equip its plane with two engines when it used to go for only one ? (Dassault with Mirage Vs Rafale for instance).

Thanks in advance for any explanation you might provide on the matter.