MD5 is a message digest / hash. It is an earlier effort by Ron Rivest. It was paired with Ron's rc5 streaming encryption cipher, but lived by itself as one of the major hash functions in 90s (md5, md160 (do I have that right :) ), and sha1). All have been weakened to different levels. md5 has real attacks where with crafted change to a message you can still get the same hash value.
Today you might STILL use sha1; it has had tremendous resiliency. NIST was expecting it to fall as badly as md5 by this point. Most use at least sha256, and sha3 is now out there. Choose your poison.
data confidentiality is another subject. Hope this helps.