An otter is a tan - two names for the same pattern. The gene that produces the pattern is called tan, <at>.She almost looks like a tan.
The Tan breed, though, is a small "running breed," very slim and racy. It also has markings that are fairly distinct from other breeds that come in the tan/otter pattern. While an otter has cream/white under its jaw, under its tail, inside its ears and on its belly, with the cream markings being lined with an edge of tan/fawn, a Tan has super high rufous factor that causes all of its markings to be bright red/mahogany. The red of its nape triangle merges with its collar markings and continues in a wide unbroken swath from its chin, down the chest and the belly, all the way to the underside of the tail. It also does not have the ticking that many tan pattern breeds do; its markings are distinct and cleanly delineated from the body color.
Here's the photo of a tan from the ARBA website Tan showing its markings and natural pose (they're a full arch breed, never pushed down or even posed, for that matter).