[AT&T, Rogers HTC One X, Telstra One XL] JSLEnterprises:
Android Debug Bridge version 1.0.29

-d - directs command to the only connected USB device returns an error if more than one USB device is present.
-e - directs command to the only running emulator. returns an error if more than one emulator is running.
-s <serial number> - directs command to the USB device or emulator with the given serial number. Overrides ANDROID_SERIAL environment variable.
-p <product name or path> - simple product name like 'sooner', or a relative/absolute path to a product out directory like 'out/target/product/sooner'.
If -p is not specified, the ANDROID_PRODUCT_OUT environment variable is used, which must be an absolute path.
devices - list all connected devices
connect <host>[:<port>] - connect to a device via TCP/IP Port 5555 is used by default if no port number is specified.
disconnect [<host>[:<port>]] - disconnect from a TCP/IP device. Port 5555 is used by default if no port number is specified.
Using this command with no additional arguments will disconnect from all connected TCP/IP devices.

device commands:
adb push <local> <remote> - copy file/dir to device
adb pull <remote> [<local>] - copy file/dir from device
adb sync [ <directory> ] - copy host->device only if changed (-l means list but don't copy)(see 'adb help all')
adb shell - run remote shell interactively
adb shell <command> - run remote shell command
adb emu <command> - run emulator console command
adb logcat [ <filter-spec> ] - View device log
adb forward <local> <remote> - forward socket connections
forward specs are one of:
tcp:<port>
localabstract:<unix domain socket name>
localreserved:<unix domain socket name>
localfilesystem:<unix domain socket name>
dev:<character device name>
jdwp:<process pid> (remote only)
adb jdwp - list PIDs of processes hosting a JDWP transport

adb install [-l] [-r] [-s] [--algo <algorithm name> --key <hex-encoded key> --iv <hex-encoded iv>] <file>
- push this package file to the device and install it
('-l' means forward-lock the app)
('-r' means reinstall the app, keeping its data)
('-s' means install on SD card instead of internal storage)
('--algo', '--key', and '--iv' mean the file is encrypted already)
adb uninstall [-k] <package> - remove this app package from the device
('-k' means keep the data and cache directories)
adb bugreport - return all information from the device that should be included in a bug report.

adb backup [-f <file>] [-apk|-noapk] [-shared|-noshared] [-all] [-system|-nosystem] [<packages...>]
- write an archive of the device's data to <file>.
If no -f option is supplied then the data is written
to "backup.ab" in the current directory.
(-apk|-noapk enable/disable backup of the .apks themselves in the archive; the default is noapk.)
(-shared|-noshared enable/disable backup of the device's shared storage / SD card contents; the default is noshared.)
(-all means to back up all installed applications)
(-system|-nosystem toggles whether -all automatically includes system applications; the default is to include system apps)
(<packages...> is the list of applications to be backed up.
If the -all or -shared flags are passed, then the packagelist is optional.
Applications explicitly given on the command line will be included even if -nosystem would ordinarily cause them to be omitted.)

adb restore <file> - restore device contents from the <file> backup archive
adb help - show this help message
adb version - show version num

scripting:
adb wait-for-device - block until device is online
adb start-server - ensure that there is a server running
adb kill-server - kill the server if it is running
adb get-state - prints: offline | bootloader | device
adb get-serialno - prints: <serial-number>
adb status-window - continuously print device status for a specified device
adb remount - remounts the /system partition on the device read-write
adb reboot [bootloader|recovery] - reboots the device, optionally into the bootloader or recovery program
adb reboot-bootloader - reboots the device into the bootloader
adb root - restarts the adbd daemon with root permissions
adb usb - restarts the adbd daemon listening on USB
adb tcpip <port> - restarts the adbd daemon listening on TCP on the specified port
networking:
adb ppp <tty> [parameters] - Run PPP over USB.
Note: you should not automatically start a PPP connection.
<tty> refers to the tty for PPP stream. Eg. dev:/dev/omap_csmi_tty1
[parameters] - Eg. defaultroute debug dump local notty usepeerdns

adb sync notes: adb sync [ <directory> ]
<localdir> can be interpreted in several ways:

- If <directory> is not specified, both /system and /data partitions will be updated.
- If it is "system" or "data", only the corresponding partition is updated.

environmental variables:
ADB_TRACE - Print debug information. A comma separated list of the following values 1 or all, adb, sockets, packets, rwx, usb, sync, sysdeps, transport, jdwp
ANDROID_SERIAL - The serial number to connect to. -s takes priority over this if given.
ANDROID_LOG_TAGS - When used with the logcat option, only these debug tags are printed.

if you look under scripting, you'll find your answer there.

its an either or, but in earlier versions of adb, it was strictly reboot-bootloader. if you have the latest sdk then it's not a problem, but who know's which version of adb some people may have (might be the adb that was packaged with a tool uploaded in 2010... you never know). Better to be safe than sorry.