The short answer
Choose MP3 for delivery, previews and everyday listening. Choose WAV when audio will be edited, mixed or passed between production tools. If you need lossless storage with smaller files, FLAC is often a better archive than WAV.
What MP3 changes
MP3 is a lossy codec. It removes information using a psychoacoustic model, then stores the result at a selected bitrate. A well-encoded 192 or 256 kbps file is practical for many listening uses, but repeated lossy encoding can make artifacts more noticeable.
What WAV preserves
WAV is a container commonly used with uncompressed PCM audio. It keeps sample values directly, which makes decoding simple and editing predictable. The trade-off is size: stereo PCM grows quickly with sample rate, bit depth and duration.
A useful workflow
Keep a lossless master in WAV or FLAC. Export MP3 copies for publishing or quick sharing. If the only source is already MP3, converting it to WAV will not restore information that the original encoding removed.