Typeform's API lives at https://api.typeform.com (api.eu.typeform.com for EU accounts).
Create a token at Account → Personal tokens. Send it as Authorization: Bearer <token>. In the examples it's written {{TYPEFORM_TOKEN}}.
Full reference: https://www.typeform.com/developers/get-started/
curl https://api.typeform.com/forms \
-H "Authorization: Bearer {{TYPEFORM_TOKEN}}"
curl "https://api.typeform.com/forms/{{FORM_ID}}/responses?page_size=10" \
-H "Authorization: Bearer {{TYPEFORM_TOKEN}}"