I received an RD on my transcript?

i just finished my first semester of college and i received an RD on my transcript for psychology, ive had an A on every ignment so far and idk about my final, i think i did good, i got an A on my midterm so i don't think i did bad, but when i got my grades i got basically all A's and then an RD? does anyone know what this means? best answer guranteed