Tere you know, tali is the same thing as talv – winter. But put together, they form a word pair used (mostly verbally) to express dissatisfaction or an unpleasant surprise similarly to: "Imagine that!" or "Hello!" (As in: you've got to be kidding). Estonians also say "Noh, halloo!", but "Tere tali! ", as well as "Tere talv!" are widely used, reflecting the fact that winter's arrival is quite often a (pleasant) surprise. Jõulud novembris? Ei noh, tere tali! (Christmas in November? Come on!)
You might've thought you spied an õige/keelsus/viga (grammar error), because in Estonian, you begin a letter with a direct personal greeting by inserting a comma: Tere, Triinu! Yup, a comma and an exclamation mark. "Tere tali" does not qualify for this rule, but Tere, kallis Mõmm! would. "Mõmm-mõmm" is the sound Estonian bears make and hence their nickname karu/mõmm, which along with kaisu/karu = teddy bear. Another pet name for a bear is mesi/käpp (honey paw), but that's another Kalev candy! And šokolaadi/tahvel and ice cream and cookie...
In addition to possibly having a calendar window to open each morning during the month of detsember or roughly the period of advent leading up to jõulud (yule), the majority of Estonian kids leave a suss (slipper) on their windowsill at nightfall starting on 1. jõulu/kuu, into which a päkapikk leaves a treat. Kalev even makes special tiny sussi/šokolaadid for this occasion, similarly to North American mini treats made for Hallowe'en, which Estonia does not have for its mardi/päev (St. Martin's Day beggars). Check out the Christmas goodies at www.kalev.eu. The advent calendar is already läbi müüdud (sold out) online.