It's called a vent pot...and it's a bad thing. In instances where dryer vent ducting is an impossibility(or just too big a project), vent pots are used to capture lint and moisture that would otherwise be expelled out a vent line (at least that's the theory). Essentially, it's venting a dryer into a bucket.
In truth, vent pots expel most of the heat and moisture back into the surrounding room. Further than the nice muggy tropical feel your home will have, vent pots can cause dangerous black mold growth and be a fire hazard due to excessive lint build up.
Even if vent duct installation is inconvenient, spend the extra effort to run a dryer vent or find a quality ventless dry system for your home. Just be sure to say no to pot!
