Questions about implicit waits in Selenium Webdriver - selenium

Question

I'm reading the docs on Implicit Waiting with Webdriver but I'm not sure I totally understand.
As I understand it,
driver.manage().timeouts().implicitlyWait(10, TimeUnit.SECONDS);
This will put in place a timeout of 10 seconds whenever looking up any element.
What, exactly, does this do?
Does it mean that when looking up any element, I will wait 10 seconds every time, even if the element is present? Or, when looking up any element, will the driver give the browser a 10-second grace period to load the element before deciding the element missing?
Since this is applied to every element, am I correct in supposing that this is just executed only once for each instance of Webdriver?

Answer 1

This will look for the element up to 10 seconds, trying to locate it every 500 milliseconds (default timeout).
From the docs
Specifies the amount of time the driver should wait when searching for
an element if it is not immediately present.
When searching for a
single element, the driver should poll the page until the element has
been found, or this timeout expires before throwing a
NoSuchElementException. When searching for multiple elements, the
driver should poll the page until at least one element has been found
or this timeout has expired.
The locating algorithm is described in W3C specifications
The Find Element, Find Elements, Find Element From Element, and Find
Elements From Element commands allow lookup of individual elements and
collections of elements. Element retrieval searches are performed
using pre-order traversal of the document’s nodes that match the
provided selector’s expression. Elements are serialized and returned
as web elements.
When required to find with arguments start node, using and value, a
remote end must run the following steps:
Let end time be the current time plus the session implicit wait
timeout.
Let location strategy be equal to using.
Let selector be equal to value.
Let elements returned be the result of trying to call the relevant
element location strategy with arguments start node, and selector.
If a DOMException, SyntaxError, XPathException, or other error occurs
during the execution of the element location strategy, return error
invalid selector.
If elements returned is empty and the current time
is less than end time return to step 4. Otherwise, continue to the
next step.
Let result be an empty JSON List.
For each element in elements returned, append the serialization of
element to result.
Return success with data result.
implicitlyWait is defined once for the WebDriver and last its lifetime.

Answer 2

Defines a wait time globally in your project. Your telling your driver to wait for n number of seconds before selenium throws an exception. If element is found earlier then the n number of seconds you mentioned, webdriver will click it once its available and dont wait for the maximum n number of seconds. It does have to wait before it throws an exception.