A pun is a verbal construction that simultaneously conveys two distinct meanings. A good, well-turned pun contains two senses that co-operate and reinforce one another, inculcating delight.
Figure 1 is an example of a good pun, specifically the Home Depot ad at the Braves' home field. "Drill one here." Yes!
Figure 2 is an example of a stupid pun. The Ottawa CBC station has an arts program called "Creative Block", because, you see, it's about creative people, and also, it occupies a block of time. You'll recall that Ottawa seriously considered adopting the slogan "Ottawa: Technically Beautiful", because, you know, the city is beautiful and has a lot of high tech industry. "Creative Block" and "Ottawa: Technically Beautiful" are akin to the driver who has turned the wrong way onto a one-way street, and is honking at the other cars. (I've seen this.) (In Ottawa.) Dumb, and broadcasting the fact.
Check here for the Atlanta picture.