An Euler path is a path that visits every edge of a graph exactly once.
Example: A postman delivering mail to every street. Each street is an edge. You want to walk each street exactly once.
If the graph has edges, your Euler path has edges (visiting vertices, possibly with repeats).
Contrast with Hamiltonian path: Hamiltonian visits every vertex once. Euler visits every edge once. These are different problems with different solutions.
Euler paths don't always exist. I'll show you the exact conditions next.