Some extramural sponsors of research projects include a category in their budget forms called participant support costs, which encompass transportation, per diem, stipends, and other related costs for participants or trainees (but not employees) in connection with relevant conferences, meetings, symposia, training activities, and workshops.
Participant support is provided by several federal agencies and other sponsors; however, the National Science Foundation has the most restrictive policies governing the budgeting, expending, and reporting of these funds.
UMB Policy on Participant Support Costs