LXP stands for learning experience platform. Where a classic LMS starts from what the company assigns, an LXP starts from the individual user. The platform suggests content based on role, interests, and what you have taken before.
In practice, the line between LMS and LXP is blurry. Most modern platforms can both assign mandatory courses and leave room for employees to find more on their own. What matters is not the abbreviation, but whether the platform fits the way you work with learning.