If you download the Pokémon directly from Pokécheck, they get given event ribbons so that you can't trade them on the GTS, and they will look cheated on the GBU, VGC etc.
However if you download the pkm file from Pokécheck (at the bottom of the Pokémon's page) you can then upload that file to pokegts.us you can receive it to your game ribbon free.
A pkm file is essentially all of a Pokémon's information put into a computer file. So what you download is the exact same Pokémon as what was uploaded.
It probably sounds like a big jump, if you've only just started online trading, but this is what everybody does because it's simply more convenient for everyone.
If you want to give out free Pokémon, you put them on Pokécheck.
If you want free Pokémon, go to Pokécheck.