Page.Validate and Page.IsValid

I have been doing a little reading about the validation controls.  I came across some information that appears to be in conflict.  Some of what I read stated that Page.IsValid calls Page.Validate thereby eliminating the need to call Page.Validate before calling Page.IsValid.  Other posts that I have read state that you always need to first call Page.Validate, followed by Page.IsValid
I would appreciate clarification.
Thanks
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