As referenced in several other posts, the Army of Rohan in full strength is comprised of several elements. As such, the Eored of The Westmark is similarly structured. Eosael is the Maegisterwigend of the Éowigend Company of the Eored of The Westmark. Continue reading if you wish to learn more about the ways of hoof and spear.
To be an Éowigend is to be a soldier in the truest sense. They comprise the vast majority of the army commanded by Theoden Thengling, King of Rohan. The sperewigends are the force behind the many eoreds positioned and operating in The Riddermark. The scouts (Cenulf's Mearcwardas) primarily provide intelligence and act as an advance team, and as such are a much, much smaller division. The Raethfinded Maegisterwigend will then report to the Aethelwigend, who nominally will then direct his Éowigend Maegisterwigend to direct his riders to smash through enemy lines, cutting a swath of destruction through the formations of and striking fear into the hearts of their enemies.
From an RP standpoint, to be an Éowigend, you must be willing to be part of a very strict military structure. Maegisterwigend commands are non-negotiable. You must uphold standards of honor and conduct yourself as a gentleman or lady, keeping your mind as focused as possible. Access to Rohan and War-Steeds are definitely preferable, but absolutely not required to be an Éowigend.