Competition: Don't Say there Isn't Any
There is always competition. (You'll lose credibility if you say there isn't any.) Somehow, people get along today without your product or service. So at the very least, the "status quo" is the competition.
So what is the status quo?
Assume Others are Targeting this Opportunity Today
You could assume that you're the only person on the planet that's smart enough to address this opportunity, or that's smart enough to address this opportunity in the way that you are targeting it. That's usually not a safe assumption. Only the paranoid survive in high-tech.
Future Competition
Who do you expect will be competition, once this market niche you're addressing is shown to be a viable niche? In other words, what bigger, established companies will enter this market? (This is not all bad news. Those larger companies who are likely to enter your market once it's shown to be viable are also companies that might acquire you; VCs know that.)
Competitive Strategy
So in the Competition section of the business plan, briefly describe the competition that you expect to have (near term and long term), and describe how you expect to win against them.
Barriers to Entry
What barriers make it difficult for other companies to compete with you? Will these barriers tend to increase over time? What can you do to increase these barriers to entry (i.e., what can you do to solidify your position so well that's it is difficult for any other company to create an advantage?)