Although the regular expression engine does not directly support the concept of the boolean AND operation it can, in a limited way, be simulated. e.g.
To search for a line containing 'error' AND 'log' the expression would be '(error.*log)|(log.*error)'. Basically the different possible combinations have been combined, i.e. find 'error' followed by 'log' OR find 'log' followed by 'error'. While this works for a small number of words it does become infeasible with a larger number of words.
Obviously the simplest way to specify an AND style expression is to use the Boolean expression engine.