Additional settings / "Terminal" tab ([Setup] menu)

Terminal size
The logical size of the terminal (numbers of columns and lines). Note that the window size (real screen size) is not necessarily equal to the terminal size.
Term size = win size
Forces the terminal size to be always equal to the window size.
Auto window resize
When the terminal size is changed, resizes the window to the terminal size.
New-line (receive)
CR
Tera Term doesn't convert it.
CR+LF
Received CR ($0D) character is converted to CR+LF ($0D $0A) pairs.
e.g.) If "CR LF" is received, it is converted to "CR LF LF."
LF
Received LF ($0A) character is converted to CR+LF ($0D $0A) pairs.
e.g.) If "CR LF" is received, it is converted to "CR CR LF."
AUTO
Received CR ($0D) or LF ($0A) character is converted to CR+LF ($0D $0A) pairs.
e.g.) If "CR+LF" are received, it is not converted.
If "CR" is received, it is converted to "CR LF."
If "LF" is received, it is converted to "CR LF."
New-line (transmit)
CR
Tera Term doesn't convert it.
CR+LF
CR ($0D) character to be sent is converted to CR+LF ($0D $0A) pairs before it is actually sent.
LF
CR ($0D) character to be sent is converted to LF ($0A) before it is actually sent.
Terminal ID
Terminal ID to be reported to the host when the host requests it. Note that the terminal ID is not identical to the telnet terminal type. To change the telnet terminal type, use the Terminal type in [Setup] Addtional Setting "TCP/IP" tab.
Local echo
Enables local echoing of characters sent.
Answerback
The string to be answered back to the host, when the ENQ ($05) character is received. Each non-printable character in the string can be expressed as a "$" and ASCII code in two-character hex number. For example, the string "ABC<CR><LF>" is expressed as the following:

ABC$0D$0A

Auto switch (VT<->TEK)
Enables auto switching between VT and TEK emulations.