Diagnosis
The laminate is durable but can be stained by certain inks and can be damaged by harsh cleaners that strip the finish.
How to Fix It
For most marks, a damp microfiber cloth with a tiny drop of mild dish soap (like Dawn) is the official safe method. Wipe, then immediately dry with a clean cloth. For stubborn pen marks, try a dry-erase marker (seriously). Scribble over the permanent ink, let it sit for 15 seconds, then wipe off with the damp soapy cloth. The solvents in the dry-erase ink can dissolve the permanent ink without hurting the laminate.
If That Didn't Work
For really set-in stains, you can try a tiny bit of isopropyl alcohol (70% or less) on a cloth, but test it in an inconspicuous spot first, like under the desk. Never use abrasive pads, magic erasers (they're micro-abrasive), acetone, or ammonia-based window cleaners like Windex on the white laminate.
Heads Up
The biggest risk isn't cleaning, it's liquids sitting at the seams. If you spill, wipe it up immediately, especially where the laminate edges meet. Water can seep into the particleboard core through an unsealed edge and cause swelling over time.