Escape pods are generally used only in the event that a ship was damaged and facing imminent destruction. Starfleet vessels were equipped with enough escape pods to allow the entire crew complement to escape the vessel.
While all escape pods had the same abilities and purpose, different types of pods were equipped with different functions depending on their deployment. For example, the escape pods installed aboard the USS Exeter in 2376 were designed to have a emergency manual override on the inside of the pods, while the USS Excalibur, another Ambassador-class vessel, had the same functions installed on the interior of the starship. (NF novel: Requiem)
Some escape pods were specialised for particular lifeforms, such as the cetacean lifeboats carried aboard Galaxy-class starships. (TNG reference: Star Trek: The Next Generation USS Enterprise NCC-1701-D Blueprints)
In the year 2373 the USS Voyager encountered a rift where various Starfleet escape pods from the Battle of Wolf 359 were found. The escape pods had come from the USS Melbourne, USS Roosevelt, USS Saratoga and others. (VOY comic: "Ghosts")
While all Starfleet vessels were equipped with escape pods, it was noted that several classes of Klingon design weren't equipped with escape pods. (ENT episodes: "Sleeping Dogs", "Bounty"; DS9 episode: "Penumbra")
In an alternate timeline where Montgomery Scott went back in time to rescue James T. Kirk before his absorption into the Nexus, former Alliance Council member Zarcot issued a distress call from a lifepod close to the Nexus. The closest vessel, the Wisdom, answered the call, and almost was destroyed by a cloaked Cardassian vessel, but Kirk and Scott warned the Supreme Arbiter of the Alliance Sarek, who was aboard the ship. (Star Trek novel: Engines of Destiny)