Rising damp is essentially a flow of water from the ground up into a wall structure. The water essentially seeps into the pores of the wall. Rising damp is common in older buildings, but can also occur in more modern buildings if your damp-proof course has been damaged. Distinctive features are discolouration that make it look like the bottom section of your wall is wet, or bumps and peeling on the wall that resembles prolonged water damage. Though it may cause unsightly aesthetic damage, rising damp can also cause a buildings structure to be compromised, and cause you much more trouble in the future.
Make sure you act fast in treating Rising Damp, if left too long you may allow mould to grow also.