Keysend:  How to find a node pubkey to send invoiceless sats to
Lnurl:  How to find an actual invoice to send sats to

A realworld analogy of paying a contractor for work:  you can either request an invoice with all the details of the work and payment destination & pay that (lnurl), or you can skip the invoice, swing by their home (pubkey) and just drop off some cash (keysend)