Brackets in a phone number typically are used to show a part of the phone number that is different from other parts of the phone number.
Their purpose can vary by country.
There is no need to enter them when dialing a phone call.
In the countries of the North American Numbering Plan (Canada, the United States, most Caribbean territories, and U.S. territories in the Pacific), brackets are used to highlight the area (geographic) code part of the phone number.
When calling from another country, always include the geographic code in the call sequence.
Even when dialing locally, especially in urban areas with multiple area codes, include the geographic code as well making a ten digit number.
Only areas with seven-digit dialing do not require the area code. However, the ten digit version (with the area code) will also work.
Outside of the North American Numbering Plan, brackets in a phone number can mean:
When brackets are around a zero, it typically signifies that the zero is a long distance trunk number. Drop the zero when calling from another country (as is the case for most countries with trunk number ‘0’ except Italy, San Marino, and Vatican City where you always dial the leading ‘0’ in the call sequence).
When there are brackets around a country code, they are there to highlight the country code.
When dialing domestically, do not include the country code in the call sequence.