Bias is someone's or something's inclination towards a specific object or point of view. Being biased towards a specific side of debate often gets in way of objectively assessing the issues at hand.
If a person's thinking is biased, they're being subjective.
Bias on Liberapedia
Liberapedia, first of all, is a resource for information on Liberal views and beliefs; and quite a lot of information is also added by liberals, so quite often the articles are liberally biased or subjective. Sometimes this bias is intentional -- as a means to parody the pretended objectivity of Conservapedia, Fox News ("Fair and Balanced", anyone?) and other Conservative media. Quite a lot of Liberapedia is written as if Liberals have no, or few, faults -- we know that's not true, but we also know there are plenty of Conservative publications that spread dirt about Liberals -- and we don't want to add to the deluge. 
(As an ending note: try to do your own research when checking biased resources to get objective information.)
- And just as Conservatives spread dirt on liberals, we do the same in return.