You see them everywhere, you know your business needs one, but just what IS a logo anyway? As with everything in life logos aren't a simple thing to explain. A logo, or what most people see as logos, aren't actually logos but ideographs, or pictographs. For example the apple graphic that Apple Inc. owns is an ideograph (also called an icon), the part that is a logo is the 'Apple' lettering also known as a logotype. The word logo is actually just a shorter way of saying logotype otherwise known as a word-mark.
Regardless of the technical terms used though, 'logo' has really just come to mean symbol, graphic or mark that represents something else (like your business). Many companies use more than one logo, take Nike for example. That swoosh is recognizable, what about the word Nike itself? Nike is able to use both of these items together and separately and they each could still be called logos even though they are technically different things. The apple icon, and the word-mark can be put together and still be called a logo, although another term could come into play and that is Lockup.
Lockups can be useful when you don't have wide spread recognition, and then split apart, and used separately, once you have that brand loyalty. Think Starbucks, for a long time their seal, or logo, was an ideograph with a word-mark built in but now their brand or icon is so ubiquitous that they don't have to present them together.
I keep all of this and more in mind when creating an identity for a company or individual, at some point in their growth they will be ready to take their brand to the next level. What is better than paying a second time to have your logo updated? That one is easy to answer, only paying once for an identity that has the potential to grow with you!