Section Characteristics

0x00000020  ('contains code')
  This section contains code. Usually set in conjunction with the executable flag (0x80000000).

0x00000040  ('has initialized data')
  This section contains initialized data. Almost all sections except executable and the .bss section have this flag set.

0x00000080  ('has unitialized data')
  This section contains uninitialized data (for example, the .bss section).

0x00000200  ('contains comments')
  This section contains comments or some other type of information. A typical use of this section is the .drectve section emitted by the compiler, which contains commands for the linker. 

0x00000800
  This section's contents shouldn't be put in the final EXE file. These sections are used by the compiler/assembler to pass information to the linker.

0x02000000  ('discardable')
  This section can be discarded, since it's not needed by the process once it's been loaded. The most common discardable section is the base relocations (.reloc).

0x10000000  ('shareable')
  This section is shareable. When used with a DLL, the data in this section will be shared among all processes using the DLL. The default is for data sections to be nonshared, meaning that each process using a DLL gets its own copy of this section's data. In more technical terms, a shared section tells the memory manager to set the page mappings for this section such that all processes using the DLL refer to the same physical page in memory. To make a section shareable, use the SHARED attribute at link time. For example "LINK /SECTION:MYDATA,RWS ..." tells the linker that the section called MYDATA should be readable, writeable, and shared.

0x20000000  ('executable')
  This section is executable. This flag is usually set whenever the "contains code" flag (0x00000020) is set.

0x40000000  ('readable')
  This section is readable. This flag is almost always set for sections in EXE files.

0x80000000  ('writeable')
  The section is writeable. If this flag isn't set in an EXE's section, the loader should mark the memory mapped pages as read-only or execute-only. Typical sections with this attribute are .data and .bss. Interestingly, the .idata section also has this attribute set.