An adjacency list of a node in a graph gives you all the nodes that are neighbors of that node. Basically an adjacency list is a node's way of saying "I can get to these other nodes starting from myself" or "Here are the nodes that I am connected to". A more concrete example is if you imagine a city (let's call it Graphville) that has roads leading to other cities next to it. Then Graphville is the node, and a list of all cities you can get to directly (i.e., not passing through other cities) from Graphville would be in Graphville's adjacency list.
A priority queue is a data structure that is like a regular queue, except that each element has a "priority" associated with it. Typically, higher-priority elements are processed before lower-priority elements in a priority queue.