There are many names for the narrative contributions that add to the story of the Era of the Dragon. They are referred to as updates, posts, submissions, and more. Perhaps the most accurate term of all is known simply as a chapter. Typically speaking a POV Chapter (point of view chapter) will be what most of the story consists of. This type of chapter focuses on a writer's main character(s) and will typically follow his/her actions within the current arc. The length of these chapters will vary, but the general idea is to provide something that is "complete". It is highly encouraged for writers to collaborate on their story updates, this helps on multiple levels to keep the narrative tied together. Finally, always keep the context of chapters in mind when writing, the things that an arc leader has said will be very important and the context of the events being equally so.
A POV Chapter is a chapter that follows the actions of and events around a single character. The updates within EotD aren't required to strictly follow a single character, but the idea is that there will be a focal character or two whom the update follows. The series A Song of Ice and Fire (among others) is a popular example of something with POV Chapters.
It is hard to pin down what exactly constitutes a "complete" chapter, but there are a few things to look for. Length is something that is often considered, but is ultimately arbitrary. A short chapter is roughly 1000 words, a medium chapter is roughly 2000 words, and a long chapter is roughly 3000 words. As for the content of the chapter itself, it should do at least one of the following groups, "Goal, Conflict, Disaster" or "Reaction, Dilemma, Decision". Rigidly sticking to these concepts isn't recommended, but they can help to determine why something doesn't feel complete (assuming that it doesn't feel complete). Further reading on this can be found here.
Collaborating on story updates is a great way to include more content and have more happen within your story. Collaboration can be as brief as "Is your character free during ___?" and "What do you think about me using the character for ___ then?", or it can be a very lengthy process where each participant plans out every detail. Neither method is necessarily better than the other, it's simply a matter of preference. Regardless, this aspect like in every aspect of EotD, collaboration is encouraged. Writing order is something else that is often unclear, simply discuss this amongst fellow writers, often times there isn't even a need to take turns (short of letting someone complete their submission).
Always keep in mind the context of what is being written in. Arc leaders will sometimes mention specific things that they would have you keep in mind, but more than those specifics, keep in mind the larger picture being presented (setting, events, timeline). There is absolutely nothing wrong with a character recalling past events not directly tied into the current events, or a character looking forward to something not in the present. Filling in bits of backstory here and there are fine, and occasionally doing larger chunks is fine as well. However, readers don't read a story for the destination, they read a story for the ride and how they arrive at the destination. This is why its important to keep in mind the current context of what is being written in. Context is key, remember that and you'll do well.
A writer will almost always be more invested in their written work than the reader. Era of the Dragon provides a chance to be both, as do most roleplays. Discuss the events of each update as well as your thought on them in the discussion topic. Most writers will spend at least an hour or two on each update, they aren't submitting their chapters with the hope that it makes no impact upon the readers. Most of our writers participate in a collaborative narrative because they enjoy the social aspects of it, and short of that it's generally getting practice in. Both groups enjoy feedback and thoughts. The chapter submissions from writers make up the core of this collaborative work, understanding how they work is monumental.