From what I recall, Sears had really helped Atari break into the home video game market with the home Pong machines in the mid 1970s, and it was even a Sears exclusive product for a short while. They were the first major retailer to give support to Atari, and like Kobun Heat said, they also handled distribution.
At the same time, though, Sears had a policy of not selling products that didn't bear the Sears name, so they came up with the name "Tele-Games" as a brand label. (This is not to be confused with the unrelated video game publisher and vendor
Telegames, which started several years later and is still around today.) When the Atari Video Computer System (the 2600 system's original name, before it was officially marketed as "2600" several years later) was released, Sears got their own version to sell, which they called the "Tele-Games Video Arcade." Atari also released their games in Sears Tele-Games packaging for the first few years. Most of the early games also had their names and box art changed for the Sears versions. Even some of the arcade game conversions had different names when sold through Sears!
Later, when very popular arcade games like
Space Invaders,
Missile Command, and
Asteroids were being ported to the VCS, Sears kept the same names, and usually the same artwork, though the box was still a Sears-style black box, rather than the variety of colors that Atari used. They eventually stopped renaming any of the games, so even original titles like
Haunted House and
Yars' Revenge would be released under those names--still in Sears boxes.
The last Sears Tele-Games cartridge to be released (in Sears packaging) was
Star Raiders in mid 1982. Incidentally, this was also the last VCS game that Atari released in their classic boxes with a wide range of colors. A month later, Atari would release their next-generation system, and the model number would be part of the name-- the Atari 5200 SuperSystem. Around that time, Atari started marketing their older VCS as the "2600," and then when the 5200 was finally released, the packaging of Atari's newly released VCS games changed to silver boxes with "Atari 2600" on them. By this time, Sears' old policy of not selling items with the Sears name was done away with, and they began selling Atari 2600 games in Atari's packaging.