'Expected Condition' in selenium, that help to find when 'ELEMENT' is visible at any time.
alert_is_present()
element_located_selection_state_to_be(locator, is_selected)
element_located_to_be_selected(locator)
element_selection_state_to_be(element, is_selected)
element_to_be_clickable(locator)
element_to_be_selected(element)
frame_to_be_available_and_switch_to_it(locator)
invisibility_of_element_located(locator)
new_window_is_opened(current_handles)
number_of_windows_to_be(num_windows)
presence_of_all_elements_located(locator)
presence_of_element_located(locator)
staleness_of(element)
text_to_be_present_in_element(locator, text_)
text_to_be_present_in_element_value(locator, text_)
title_contains(title)
title_is(title)
url_changes(url)
url_contains(url)
url_matches(pattern)
url_to_be(url)
visibility_of(element)
visibility_of_all_elements_located(locator)
visibility_of_any_elements_located(locator)
visibility_of_element_located(locator)