tdf file synopsys
tf define the technology info of the process u using. like metal layers, res,cap, pitch and so on, too much to say , refer to the file provide by the Astro guide.
gdsii is a binary format which stores the layout info. u use this format to tapeout ur chip usually. Using gdsii , u can generate the detail cell view in milkyway.
db is synopsys specific format . u can store the design in this format , and tranform the lib to db format.
sdc is a constraint file , which usually contain the clock specification , multicycle path definition and some other design constraint, if u know synthesis , u know that.
EDIF is netlist format .