The ranger is among the fastest ground units used in the war. As the war continued, their design was standardized among the Allied nations for easy construction and maintenance.
Fast and lightly armored, this unit is ideal for scouting an area quickly. Used as a support unit for an infantry squad, the Ranger can soften up the enemy before a direct confroI antation occurs. - Red Alert manual(src)
The Ranger is cheap and easy to produce. It can be used as a scout to explore the battlefield and to harass enemy bases especially when in conjunction with Light Tanks. It is also effective against infantry, but it can not crush them. It is the first vehicle available to the Allies in the campaign. However, it possesses virtually no armour, which renders it vulnerable to any foe other than infantry. They are also unable to deal with air units. Interestingly, Ranger cannot transport infantry in-game, so an APC is required for this purpose, probably due to protection issues.
In the beta version of the game, the Ranger is known as the Jeep, but was likely renamed to avoid copyright issues with Chrysler.
The sprite resembles a Willys MB/Ford GPW or M38A1, while the rendered versions are modeled after a Jeep Wrangler YJ (the first generation Wrangler). The Remastered version bears a much closer resemblance to the WWII-era Willys/Ford Jeeps.
Although in-game it is an exclusively Allied unit, two cutscenes showed the Soviets using Rangers, most likely representing a GAZ-67 or similar vehicle.