A gradient background usually refers to an background of a particular color/tone that changes value from light to dark giving a uniform look while preserving some sense of depth due to the transition in the value. Portrait photographers use this often, as in the attached sample. In this case the background was a printed piece of plastic sheet available in photo supply stores like Calumet. Otherwise using an application like Photoshop, you can silhouette your subject on to it's own layer and create a new layer where you can "paint" a tonal gradation of any color using the tools available to you. It's one of several things you can do to get rid of an ugly or busy background.

Example of gradient background

The dog picture is definitely the stronger of the two images. Mostly thanks to the shallow depth of field. I think having some grass in front (out of focus) helps establish the environment and tells the story: the dog is in his element. Having the dog backlit helps the emotion of the shot as well. Compositionally, the pooch is smack-dab in the middle, which is a little static. You could crop off a few inches on the right bringing his head closer to the right side of the frame for more effective cropping and a stronger photo.
Cats, like children, want attention and having their picture taken. So they mess with you and say " aren't I cute? Shoot Me!" I would guess it was one of those situations. It's basically a snap-shot and that's OK.... Keep shooting and have fun.

Minolta color meter II with flash sensor - used little. Great for when you have to white balance multiple flash heads or light sources, or when you want your flash to be the same white balance as the ambient light in a room. Used with available Roscoe color correction gels it can be a life saver. Comes in original packaging with instructional manuals for both the Color Meter II and III. Originally $1000. Asking $500.

A flash meter is really essential for consistent results. I meter each light in my set-up to establish highlight, shadow, ambient and fill in various areas of my set or subject. The inverse square law is a hard and fast rule and is always a good starting point. You make adjustments based on what the light is falling on; how absorbent or reflective, etc. If you're shooting a group with an umbrella or soft box, light the closest subject with the edge of the projected light saving the center (and brighter) output for those further away from the light. If you're using two lights and you have some "depth" to play with, make one side a little lighter than the other, creating a highlight and shadow scenario. The difference can be as little as a half-stop and you'll add some depth to the shot as opposed to the "copystand" lighting effect.