hasOne or BelongsTo in Laravel?

I have two tables: Photos and ProductPhotos where ProductPhotos is:

ProductPhotos
_______________
product_id | photo_id

And Photos is:

Photos
_______________
id | photo

Does it mean that relation beetween ProductPhotos -> Photos as belongsTo or hasOne yet?

Cause photo_id is foreign key, I guess it is belogsTo

via Chebli Mohamed