It increases the damage the aliens' slot one weapons do significantly (bite for lerk and skulk, spit for gorge, swipe for fade and gore for onos). However, it also decreases how often you can attack to compensate. So if you're not accurate with bite, it might be an idea not to use focus, since you'll won't be able to fire it off as often.
The actual figures seem to depend on who you ask. :/
<!--QuoteBegin--[FFT]Cartman2b+Jan 10 2004, 09:04 AM--></span><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td><b>QUOTE</b> ([FFT]Cartman2b @ Jan 10 2004, 09:04 AM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> Theres been loads of posts about this in general discussion =) <!--QuoteEnd--> </td></tr></table><span class='postcolor'> <!--QuoteEEnd--> This is one of them. <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html/emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif'><!--endemo-->
This thread <a href='http://www.unknownworlds.com/forums/index.php?act=ST&f=1&t=58481&hl=focus' target='_blank'>here</a> is on focus a search of "focus" would have got the results you wanted.
Comments
The actual figures seem to depend on who you ask. :/
This is one of them. <!--emo&:p--><img src='http://www.unknownworlds.com/forums/html/emoticons/tounge.gif' border='0' style='vertical-align:middle' alt='tounge.gif'><!--endemo-->
- RD <!--emo&:)--><img src='http://www.unknownworlds.com/forums/html/emoticons/smile.gif' border='0' style='vertical-align:middle' alt='smile.gif'><!--endemo-->
edit: focus replaces pheromones