I just finished testing my site and competitors sites in seodigger.com . What exactly does weight and OT mean? should I aim to rank higher on keywords that hold more weight ?
OT is Oveture keyword popularity. Since the Overture keyword tool disappeared a little while back, I assume they are referencing older Overture stats that they saved to a database. WT is the keyword popularity in WordTracker. So both of these columns just refer to how popular these keywords (how many people search for the keyword). Neither value will be an accurate estimation though. It is best used as a relative number to compare against other keywords. Yes you should aim to rank higher for more popular keywords. The higher the search volume, the more traffic and revenue you can get.
Are you referring to keyword density weight/importance? In that case here's a short explanation. Keywords in titles matter way more than keywords in headers which matter way more than keywords in body text For more information, you may check this keyword density analysis tutorial.
WT in seodigger means wordtracker while OT means Overture. I don't rely on the WT and OT results. I check the traffic of the keywords on keyword discovery.