An action that has not happened yet.
An action that has not happened yet, but after a point, will have happened.
An action that is completed, but you time traveled to the past, and so it's not happend yet.
An action that was been completed, but you decided to keep doing it anyway so it's not really complete.
Another crazy explanation.
1st P. Part
2nd P. Part
3rd P. Part
4th P. Part
5th P. Part
-o, -s, -t, -mus, -tis, -nt
-bam, -bas, -bat, -bamus, -batis, -bant
-eram, -eras, -erat, -eramus, -eratis, -erant
-ero, -eris, -erit, -erimus, -eritis, -erint
-i, -isit, -it, -imus, -itis, -erunt
To will have ____.
To had ____..
To be ____.
To keep on ____ing.