The main distinction is rosin core vs. acid core. Always use some sort of rosin core, NEVER use acid core on any electronics. Acid core will eat away the connections/traces on the pcb. Flux is also a good idea when soldering delicate components.
You know what I dont get? When I tin my Iron *placing solder on the bit* it just blobs solder in little circles and doesnt flow on the bit and get everywhere it sticks in a packed bubble circle... How do I properly get it to flow all over the bit?