Basically Spike and Xander are together but Xander is unsure why Spike is with him, and Spike thinks Xander doesn't love him as Xander keeps trying to distance himself from the relationship so he does not get hurt. Neither of them would tell the others (Buffy, Willow etc..) about the relationship because they believed that the other did not want to tell. It was really sad and a bunch of not understanding and it was giles I think that finally told them that they where not fooling anyone and to get over it and be together.
Thanks in advance