A lecture was a type of speech presenting information in an educational setting.
James T. Kirk recalled hearing lectures about the Nomad probe at the Starfleet Academy. (TOS: "The Changeling")
In 2374, Ezri Dax received a fifteen minute lecture from the surgeon of the USS Destiny before being joined with the Dax symbiont. (DS9: "Shadows and Symbols")
Jean-Luc Picard was known, among other things, for having lectured. (PIC: "Remembrance")