there are various settings, but the quality is very good, you wouldn't really tell a difference, but there is a slight quality loss (to my understanding)
Handbrake is a video transcoder... which means it will decode a file, and then re-encode it into a different format. DVDs are encoded using MPEG-2 which is a fairly old technology and was invented back when more effective encodings were unpractical. Any time any lossy encoding is unencoded and then re-encoded... then some image loss will occur.
Most people now encode using MPEG-4 (H.264). It has about the same quality as MPEG-2, but results in significantly smaller file sizes. MPEG-4 was not economically feasible back when DVDs were invented. One of the most common uses of Handbrake are to convert MPEG-2 DVDs to MPEG-4 (H.264) files. You are very unlikely to notice any significant image degradation... but you can fit a lot more videos on your devices.
/Jim