Line height and hand control
The toddler setting prints letters close to an inch tall. Large letters are not a stylistic choice: a child who does not yet have fine motor control writes from the shoulder and elbow, and needs the room.
Preschool halves that. Elementary brings it down to something near normal ruled paper, at which point the sheet is practice rather than instruction, and fits six repetitions to a line.
Choosing a guide style
Solid prints the letter in pale grey to be written straight over. It is the easiest, and the one to start with, because the child never has to guess where the stroke goes.
Dashed shows the letter as a broken outline, so the hand has to carry the stroke between marks. Dotted is the sparsest and closest to writing unaided; it works as the last step before removing the guide entirely.
The three line system
Each row has a solid top line, a dashed middle line and a solid baseline. The dashed middle marks the x-height, which is where lower case letters without ascenders stop.
That middle line is what makes letter proportion teachable: an 'a' that reaches the top line is wrong in a way a child can see for themselves, without being told.
Print or cursive
Print is where handwriting instruction starts, and it is what almost every worksheet request means. The letters are separate, which lets a child concentrate on one shape at a time.
Cursive is introduced later, typically once print letters are formed reliably. These sheets present cursive one letter at a time rather than joined into words, because the first thing to learn is the shape of each letter and its entry and exit strokes.
About the letterforms
Print letters are set in Andika, a typeface designed for literacy teaching, with the single storey 'a' and 'g' that primary handwriting instruction uses. The double storey forms in most text faces are not what children are taught to write.
Cursive uses Playwrite US Traditional, from a type project built specifically around school handwriting models rather than around decorative script.
Letter shapes are embedded in the file as outlines rather than as text in a font, so a worksheet prints identically everywhere and does not depend on anything being installed.