OpenVPMS allows the use of the 'wildcards' % and _ (underscore). % means any number of characters, _ means one character.
Thus a%b will find everything starting with 'a' following by zero or more characters, then a 'b'. There is also an implicit % added at the end of what you enter.
Hence a%b will find Abbie, Abe, Amber, and Annabelle. Note that the case you use does not matter, ie A%B will find the same names.
Using sm_th will find Smith and Smyth but not Smooth.
Note that since an implicit % is added to what you enter, leaving the Search field empty is equivalent to entering % and this will find all records.