$args = array(

    'post_type' => 'post',

    'tax_query' => array(

        array(

            'taxonomy' => 'people',

            'field'    => 'slug',

            'terms'    => 'bob',

        ),

    ),

);

$query = new WP_Query( $args );

$args = array(

    'post_type' => 'post',

    'tax_query' => array(

        'relation' => 'AND',

        array(

            'taxonomy' => 'movie_genre',

            'field'    => 'slug',

            'terms'    => array( 'action', 'comedy' ),

        ),

        array(

            'taxonomy' => 'actor',

            'field'    => 'term_id',

            'terms'    => array( 103, 115, 206 ),

            'operator' => 'NOT IN',

        ),

    ),

);

$query = new WP_Query( $args );

$args = array(

    'post_type' => 'post',

    'tax_query' => array(

        'relation' => 'OR',

        array(

            'taxonomy' => 'category',

            'field'    => 'slug',

            'terms'    => array( 'quotes' ),

        ),

        array(

            'taxonomy' => 'post_format',

            'field'    => 'slug',

            'terms'    => array( 'post-format-quote' ),

        ),

    ),

);

$query = new WP_Query( $args );