TCP analysis / interpertation - ACKs and lost segments

Hi,

I'm trying to perform TCP analysis, or at least learn how to do it, and I would really appreciate some information about the following filter fields.

tcp.analysis.ack_lost_segment tcp.analysis.lost_segment tcp.analysis.duplicate_ack tcp.analysis.retransmission

I'm not really sure about the first two, since I've read in some places that they might be due to drops in Wireshark while capturing, and might not be a real issue of the TCP stream. This is somewhat confusing :(

Thank you in advance!