A Christmas film, as its name suggests, is a movie where the plot centers around the Christmas holiday, and is usually released (or shown in rebroadcast) between Thanksgiving and Christmas (the time frame in which most of these films are shown).
In American filmmaking, such a film makes frequent use of stock characters: the lead actor/actress has "lost the Christmas spirit" (commonly the person has experienced a tragedy, such as the loss of a loved one, around Christmas), is frequently a single parent, and who is often a resident of a large city who has to travel (sometimes not willingly) to a much smaller town, usually hoping to leave as soon as possible. The other lead actor/actress (always of the opposite gender) shows a romantic interest and commonly has befriended the child(ren) of the single parent, hoping that they will convince their mom/dad to make the relationship work. Other family members and or "new friends" of the town make attempts to help bring Christmas joy back to the one who has lost it, as well as to convince him/her to relocate to the small town.
American cable channels Hallmark Channel and Hallmark Movies & Mysteries Channel will broadcast Christmas films non-stop between Thanksgiving until a few days after Christmas, along with promotions during the summer season (announcing the new lineup for the upcoming season).