Query an ArcGIS feature server?

[SimpleGuy]

The following code was used earlier to query data and I got the URL by inspecting a page element with a table in it. So I figured why not try to figure out how this works so I can use it on other websites to pull large amounts of information. But I'm having trouble.

data_url = 'http://sagisservices.thempc.org/saint/rest/services/OpenData/Parcels/MapServer/0/query?objectIds=1%2C2%2C3%2C4%2C5%2C6%2C7%2C8%2C9%2C10%2C11%2C12%2C13%2C14%2C15%2C16%2C17%2C18%2C19%2C20%2C21%2C22%2C23%2C24%2C25%2C26%2C27%2C28%2C29%2C30%2C31%2C32%2C33%2C34%2C35%2C36%2C37%2C38%2C39%2C40%2C41%2C42%2C43%2C44%2C45%2C46%2C47%2C48%2C49%2C50%2C51%2C52%2C53%2C54%2C55%2C56%2C57%2C58%2C59%2C60%2C61%2C62%2C63%2C64%2C65%2C66%2C67%2C68%2C69%2C70%2C71%2C72%2C73%2C74%2C75%2C76%2C77%2C78%2C79%2C80%2C81%2C82%2C83%2C84%2C85%2C86%2C87%2C88%2C89%2C90%2C91%2C92%2C93%2C94%2C95%2C96%2C97%2C98%2C99%2C100&outFields=*&returnGeometry=false&orderByFields=&f=json'
response = requests.get(data_url)
response.raise_for_status()
data = response.json()

So I just figured out that I can access a webpage with a list of (featureservers) for ARCGIS here: https://services1.arcgis.com/O1JpcwDW8sj...t/services

What am I actually doing when I send a Query that looks like this to the server:

data_url = 'https://services1.arcgis.com/O1JpcwDW8sjYuddV/ArcGIS/rest/services/2015_Feature_241/FeatureServer/0/query?objectIds=1%2C2&f=json'
response = requests.get(data_url)
response.raise_for_status()
data = response.json()

I know that /0 is the index to access the first feature 2015_feature_241,
I know that /query?objectIds is telling it which information I want,
I know that f=json formats the output to json.

What I don't know is how to pull all the information for feature 2015_feature_241. The only reason I put in objectIds=1%2C2 is because I saw that it worked for my previous example but I dont know what it is doing. Could anyone point me in the correct direction to read up on the syntax for querying?