Most term sheets will require founders, executives and certain other employees (usually developers, designers and technical employees) to sign Confidential Information and Invention Assignment Agreements. These agreements do two primary things.

Invention Assignment. Most importantly, they require the founders and other employees to give all of the intellectual property they develop while working with the company (either before or after the agreement) to the company. This is important to make sure that the company has all of the rights to the IP being developed and to prevent employees from later claiming that they individually own the rights.

Confidentiality. Prevents employees from disclosing confidential information to people outside of the company or using confidential information for purposes other than working for the company - e.g., developing another company or working for a competitor.

These provisions generally don't cause much concern for founders. If you had a lawyer during formation of the company, you'll probably already have these agreements in place to protect the Company's intellectual property. They're good for the company and there's no need to wait for a financing to get them set up. If you don't have them, agreeing to them during a financing is just a way to clean house.

Have your lawyer look over the proposed agreements to make sure that they're reasonable. The major negotiated point is usually the scope of the intellectual property given to the company. Some employees who work on other projects won't be willing to give up intellectual property that they created on their own that isn't related to the company's business. You should be able to work out reasonable agreements with each of the founders, executives and employees to get company IP assigned.