What does it mean that my pistol is a double action gun it's a ruger p345?

Its the first gun I ever owned and its legally registerd to me I keep googling information about it but havent found answers for my exact questions or

It's the first gun I ever owned and it's legally registerd to me I keep googling information about it but haven't found answers for my exact questions

or:It's the first gun I ever owned and it's legally registerd to me I keep googling information about it but haven't found answers for my exact questions

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