Difference between meta name title tag and title title tag

Please clarify what is the difference between <meta name="title"> tag and <title></title> tag.

<title>Page title</title>
<meta name="title" content="Page title">

If both are used which is most prioritised?

I observed some sites both meta tag title and <title></title> tags both are same,which is expected, please confirm?

If we didn't use <meta> tag title would I have any problem regarding SEO?

<head>
<title>Stackoverflow</title>
<meta name="description" content="free source">
<meta name="keywords" content="HTML,CSS,XML,JavaScript">    
</head>

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