Is Cache and Stack the same thing?

Assuming you are talking about processor internals...

They are not the same thing, even when they are implemented with the same technology. Cache is "content-addressable memory" where entries are replaced in least-recently-used order. This is always the fastest memory technology available to the processor for the size of the cache memory, holding temporary copies of recently used main memory.

A stack stores information in "last-in-first-out" order, so it's the *most recently used* entries that are removed first. The stack that's visible to the programmer is generally stored in main memory, rather than in high-speed memory visible only to processor hardware. However, other stacks may be used internally for handling multiple concurrent interrupts or other perhaps hardware events and actions.

There may or may not be a hierarchy, but if there is it will certainly be cache memory that is consulted first to satisfy a request for a word from main memory. That will happen before access to a software stack stored in main memory.

They are both stored in your RAM chips.