Niagara Falls is the collective name for three different waterfalls.
Two are on the US side of the border and the third is Canadian.
There's the Horseshoe Falls, otherwise known as the Canadian Falls.
It's the one in all the tourism pictures:
Link - http://www.niagarafallslive.com/images/HorseshoefromSkylon.jpg
Then there's the butt-ugly American Falls and smaller Bridal Veil Falls beside it:
Link - http://upload.wikimedia.org/wikipedia/commons/0/09/Niagara_American_Falls.jpg
On the US side, there's some outlet malls and cheap motels.
And a lot of urban decay: boarded up homes, rusting old factories, etc.
On the Canadian side, Niagara Falls Ontario is a thriving international tourist mecca complete with casinos, indoor waterpark, and all sorts of other attractions besides the Falls themselves.
And within a short drive there's Marineland (similar to Sea World), the Niagara Wine Region dotted with quaint B&B's, resorts, orchards and vineyards and wineries (complete with tasting tours), historic War of 1812 battlefields, and picture-postcard towns like Niagara-on-the-Lake:
Link - http://apillowandtoast.com/images/attractions.jpg
Link - http://teardroptravelin.files.wordpress.com/2011/06/just-one-example-of-floral-excess-in-niagara-on-the-lake.jpg?w=640&h=477
Best advice is to google Niagara Region tourism and indulge yourselves.
Passport cards are cheaper than passport books, and acceptable for crossing the border by car.