grid\GridView $columns

Grid column configuration. Each array element represents the configuration for one particular grid column. For example,

[
    ['class' => SerialColumn::className()],
    [
        'class' => DataColumn::className(), // this line is optional
        'attribute' => 'name',
        'format' => 'text',
        'label' => 'Name',
    ],
    ['class' => CheckboxColumn::className()],
]

If a column is of class yii\grid\DataColumn, the "class" element can be omitted.

As a shortcut format, a string may be used to specify the configuration of a data column which only contains attribute, format, and/or label options: "attribute:format:label". For example, the above "name" column can also be specified as: "name:text:Name". Both "format" and "label" are optional. They will take default values if absent.

Using the shortcut format the configuration for columns in simple cases would look like this:

[
    'id',
    'amount:currency:Total Amount',
    'created_at:datetime',
]

When using a $dataProvider with active records, you can also display values from related records, e.g. the name attribute of the author relation:

// shortcut syntax
'author.name',
// full syntax
[
    'attribute' => 'author.name',
    // ...
]