A license is not a transfer of intellectual property; it is a promise not to enforce the property against the person holding the license, and almost every hard question in IP licensing follows from that single insight. This UpLaw guide walks the full anatomy of a license agreement: the grant clause and its variables (exclusive, sole, and non-exclusive; field of use; territory; term; sublicensing and have-made rights), and how the analysis shifts depending on whether the licensed right is a patent, a copyright, a trademark, or a trade secret. It explains the traps unique to each regime — the naked-licensing forfeiture that can destroy a brand, the Section 204(a) writing requirement that voids an unsigned exclusive copyright license, patent exhaustion after Impression Products, and the reality that a trade secret license is only as valuable as its confidentiality covenant. It then works through the money: running royalties, lump sums, milestones, minimums, stacking, the post-expiration royalty bar of Brulotte v. Thys and Kimble v. Marvel, audit rights, and the drafting devices that survive them. Finally it covers improvements and grant-backs, diligence obligations, representations and indemnities, most-favored-nation clauses, assignment and change of control, termination and survival, bankruptcy under Section 365(n) and the Mission Product v. Tempnology rule for trademarks, and the antitrust and misuse limits on what a licensor may demand. A running hypothetical — a single deal licensing a patent, a brand, and software to one licensee — carries the doctrine from grant clause to wind-down.