AThreet,
CRM has 3 types basically, Note, Post, and Activities, you can see three of them in the Social Pane, right.
They are totally different are used for different reasons and purposes as well.
In practice, let's have analogy.
Let's say you visit your customer through Appointment (one of Activities), then you found something useful, or let's say you are watching movie then found something useful about one of your client, what will you do?
There are three things you can do if you map with CRM features
First, you can TAKE A NOTE, like you are in the Requirement Meeting with client, you use NOTEPAD or your smartphone to take a note. Then this is you are doing is writing Notes, in Notes you also can have attachment, so either the users are using and writing in the CRM Notes directly, or use Notepad then latter just put as attachment in the Note, then you also can create Word and PDF Documents as well.
Notes based on its table name Annotation contains information that you need to take note and you can attach files as well. This is the fundamental different thing, Note is identic with Annotation, Information, and Attachment. You can also attach .zip and .rar files as well.
Second, you can POST something like you always keep updated and keep exists in the Social Media, you POST something about your clients that is very important for other users to notice it and yourself to keep updated, while note just for keeping information in case you forget and for history as well, while POST purposely to keep yourself, your manager, your team keep informed and updated, stay abreast with the current condition.
POST in CRM identic with Social Communication and Activities, which you can INVITE others to comment and Like as well, while Note, it is not purposely for you to make other people notice and comment or even like it. And for some occasions, it is very important to use Post in CRM to always keep posting automatic once Opportunity created, once Opportunity Won, or Opportunity Lost, so people in Organization can be aware and stay abreast.
While, NOTE, is not very important right you create rule every time Opportunity created then create Note, no one will notice NOTE more than POST, because you need to open one by one the Account, usually you don't put Note in any Dashboard at all.
Third, you arrange next Activity, can be Phone Call, Appointment after successful meeting to approach this prospect closer and closer every second.
Keeping creating NOTE and keeping POSTING to anyone without any Activities to the Client itself wont help the users to approach customer, get customer, and gain revenue. So that you need interaction, interaction, and interaction with Customer.
You can also create TASK as one of the activity, it is another feature potentially make confusion, but the point here is you create a to do list, like Appointment by not arranging exact time to meet, you just set goal to yours, then you set schedule when you would complete this Task, you create TO DO LIST to make sure that you will always remember your Client view and also you can ASSIGN Job and Task to other users, to subordinates for example, while POST and NOTE are not mainly to give assignment to others.
Hope this can help you!
Thank you.