https://docs.magento.com/m2/ce/user_guide/design/header.html

Header

The Header section identifies the path to your store logo, and specifies the logo alt text and welcome message.

店舗ロゴのパスを定義し、ウェルカムメッセージを定義します。

To configure the header:

1.

On the Admin sidebar, tap Content. Then under Design, choose Configuration.

2.

Find the store view that you want to configure. Then in the Action column, click Edit.

3.

Under Other Settings, expand  the Header section.

4.

Make any changes necessary to the logo and welcome message settings.

5.

When complete, tap Save Config.

• Field Descriptions

  FIELD	SCOPE	DESCRIPTION
  Logo Image	Store View	Identifies the path to the logo that appears in the header. Supported file types: PNG, GIF, JPG (JPEG)
  Logo Attribute Width	Store View	The width of your logo image in pixels.
  Logo Attribute Height	Store View	The height of your logo image in pixels.
  Welcome Text	Store View	The welcome message appears in the header of the page and includes the name of customers who are logged in.
  Logo Image Alt	Store View	The Alt text that is associated with the logo.