The Latin Words program takes a few seconds to initialize itself, then you can type a word into the
input box. If what you have typed is a valid Latin word (i.e. it occurs in the list of word forms from POL) the background of the input box changes to a shade of green, otherwise the background is a shade of red.
The program checks the word list for every letter you type, so if you type in 'tertium', say, you will see the background colour change several times:

T - red
E - green (TE is a good Latin word)
R - green (TER is good)
T - red (no Latin word TERT)
I - red
U - red
M - green
(yes, TERTIUM is an acceptable Latin word)