What is the difference between SMD and pad in Eagle?
Can I use both to solder?
I am trying to make a PCB for my LEDs and I don't know I have to use SMD or pad.
Both are technically "pads". The difference is that "pad" if for thru-hole components, so has a hole in it. In eagle, this hole becomes a integral part of the pad. "SMD" is for surface-mount components, so has no hole thru it.
There are two types of component packaging available in the market. SMD and thru-hole.
The PCB that you are making for LED's is most probably equipped with thru hole LED. (If you are asking this question it leads me to think that you don't know the difference between Chip LED and thru hole. So my assumption is that you are making hobbyist stuff. )
Image Courtesy - Wikipedia
If your LED looks something like above, you need to use Pads in your design which are thru hole. Instead of SMD pads.
To answer this question satisfactorily, i need you to ask that did you make the schematic design of your board?
If yes, then you would have chosen LED such as LED 5mm or LED 3mm or ChipLED in eagle symbol selection. If you did the above step, your question is void.
SMD is a form factor for a component (as opposed to thru-hole). A pad is what the pins of an SMD component rest on to be soldered.
Presumably (I haven't used eagle pcb specifically), SMD is used to add an entire component to the layout, while pad is used for extraneous things, such as heatsinking.