Meaning of the various symbols in .aspx page of asp.net

I have come across different symbols in .aspx page of asp.net

<%#eval(expr) %> 
<%#bind(expr) %>
<% %>  - for specifying the c# code in aspx page
<%$ %> - for specifying the SQL connection string in <asp:SqlDataSource>

Is there any underlying logic behind these symbols or is it just syntax which we have to remember blindly? What does <% %> mean in general ?

Please help me.

Thanks in anticipation