The four proxy-group types: select, url-test, fallback, load-balance

The groups on the Proxies page are "proxy groups". When a rule targets a group, the group's type decides which node actually carries the traffic:

• select (manual): the most common type — you pick, it obeys. Good as the top-level entry group;
• url-test (auto-best): periodically tests all members and uses the fastest. Great when node quality fluctuates, but it may bounce between two nodes, changing your exit IP;
• fallback (failover): uses the first available node in list order and only moves on when the current one dies. Ideal for a "primary + backup" stability-first setup;
• load-balance: spreads connections across several nodes — see "The two load-balance strategies".

Example

proxy-groups:
  - name: Auto
    type: url-test
    proxies: [HK-01, HK-02, JP-01]
    url: http://www.gstatic.com/generate_204
    interval: 300

interval is the re-test period in seconds. Both url-test and fallback need url and interval to function. Subscription users do not have to write any of this — the provider already did; knowing the meaning is enough to read the Proxies page structure.