rs id is reference SNP cluster ID see here. It's basically a unique identifier.
This table is taken from your link:
rs position 0 1
rs11089130 14431347 C G
rs738829 14432618 A G
rs915674 14433624 A G
The allele codes are the 3rd and 4th columns. An SNP is site where a different base is found in different versions of the same gene (different versions of genes are alleles). For a given SNP the different alleles are referred to as the 0 or the 1 allele. So in the table the first SNP, rs11089130, has two alleles: allele 0 has a C at the SNP position (14431347) whereas allele 1 has a G at that position. The allele code does not imply any biological significance.
I'm not sure what would happen if there were three alleles at an SNP, but presumably there would then also be an SNP coded as 2.
Edit: Allele 0 is the residue from the reference genome. Allele 1 is the residue being studied, the SNP.