Outlook4Gmail is an Outlook plug-in, which enables you to synchronize Outlook contacts with Google contacts. If you often use Outlook as mail receiving and sending software and are a fan of Google, Outlook4Gmail will suit you.
After installing Outlook4Gmail and restarting Outlook, you can see many Outlook4Gmail tags in the above tab bar. The functions inside are straightforward, such as synchronization, selecting synchronization mode, account number, record, import, export, etc. You need to click the account button to enter Gmail's account password. Advanced settings need to be set in Outlook options.
There are one-way Outlook -> Gmail, Gmail -> Outlook, and two-way synchronization, including contact names, addresses, mailboxes, birthdays, notes, and so on.